This invention generally relates to integrated circuitry and in particular to voltage level translator circuitry implemented in integrated circuitry.
There may be many instances involving integrated circuitry that require the use of voltage level translators to interface circuitry that operates at different voltage levels. For example, a first circuit may transmit voltage signals ranging from a ground voltage VSS (e.g., a “LOW” voltage signal) to a source voltage VCC (e.g., a “HIGH” voltage signal). A second circuit receiving these voltage signals may only register “HIGH” voltage signals that exceed VCC. Therefore, a voltage level translator is interfaced between the first and second circuits to translate VCC to a higher voltage VCCP so that the second circuit recognizes the VCC signal provided by the first as a HIGH signal.
As another example, voltage level translators may be used to translate the ground voltage VSS to a lower voltage VBB. In this case, the voltage level translator may interface a first circuit, which provides a VSS signal, to a second circuit, which does not recognize VSS. Therefore, in order for the second circuit to recognize that the first is providing a LOW signal, the voltage translator changes VSS to VBB.
Conventional voltage translator circuitry that accomplishes the above-mentioned voltage level translations are known. However, current design trends involving integrated circuitry is rendering conventional voltage translators obsolete. This is because the source voltage, such as VCC, being used in integrated circuitry has decreased to such an extent that existing voltage translators cannot function properly. For example, as source voltages approach 0.8 volts and below, transistors in conventional voltage translators do not turn ON because the source voltage is too low to overcome the voltage threshold needed to activate such transistors. Moreover, even if transistors are used that can be turned ON with low source voltages, conventional circuitry topology does not provide protection against gate oxide breakdown, punch-through, and channel-hot electron effect (e.g., a form of tunneling).
It would therefore be desirable to provide voltage level translation circuitry that operates at low source voltages.